1. Field of the Invention
The present invention relates to a developing apparatus for developing a latent image with a non-magnetic developer, more particularly to an apparatus of the type wherein a thin layer of a non-magnetic developer is formed on a developer carrier or a sleeve.
2. Description of the Prior Art
Conventionally, various types of apparatus have been proposed and put into practice as to a dry type one-component developer apparatus. However, in any of those types, it has been very difficult to form a thin layer of one-component dry developer, so that a relatively thick layer of the developer is used. On the other hand, the recent device for the improved sharpness, resolution or the other qualities has necessitated the achievement of the system for forming a thin layer of one-component dry developer.
A method of forming a thin layer of one-component dry developer has been proposed in U.S. Pat. Nos. 4,386,577 and 4,387,664, and this has been put into practice. However, this is the formation of a thin layer of a magnetic developer, not of a non-magnetic developer. The particles of a magnetic developer must each contain a magnetic material to gain a magnetic nature. This is disadvantageous since it results in poor image fixing when the developed image is fixed on a transfer material, also in poor reproducibility of color (because of the magnetic material contained in the developer particle).
Therefore, there has been proposed a method wherein the developer is applied by cylindrical soft brush made of, for example, beaver fur, or a method wherein the developer is applied by a doctor blade to a developer roller having a textile surface, such as a velvet, as to a formation of non-magnetic developer thin layer. In case where the textile brush is used with a resilient material blade, it would be possible to regulate the amount of the developer applied, but the applied toner layer is not uniform in thickness. Moreover, the blade only rubs the brush so that the developer particles are not charged, resulting in foggy images. It should be noted that the non-magnetic developer particles cannot be conveyed by magnetic force since they are not influenced by magnetic field.